Intel Pentium 4 "Prescott" to be Slower than "Northwood"?

Performance of highly-anticipated code-named Prescott processor, the third-generation NetBurst microprocessor from Intel, may appear to be generally slower than speed of currently available Pentium 4 “Northwood” chips. The reason for that is deep pipeline implemented to bolster clock-speeds of the CPU.

According to a report from ZDNet, industry sources anticipate Prescott’s pipeline to feature about 30 stages, 10 more compared to Northwood core.

Deeper pipeline allows dividing each command into smaller parts, which appear easier and faster to execute than the entire command. Such approach allows to pump up the clock-speeds, but will lead to increased overall time required for execution of each command and also cause some delays as a consequence of branch mis-prediction and necessity to reload the pipeline..

Historically CPU makers have been enlarging pipelines, though, because of massive efforts to improve performance, both architectural and clock-speed related, the impact of deeper branch was not too dramatic. The only time a company was criticized for too deep pipeline was in 2000, when Intel released its original Pentium 4 “Willamette” processor that fell behind competing AMD Athlon CPUs in terms of performance. Though, being able to rapidly ramp the clock-speeds, Intel’s Pentium 4 CPUs got performance crown in mid-2002 with its Pentium 4 processors at 2.53GHz. Unfortunately, high core frequencies lead to massive power consumption what may potentially limit maximum clock-speeds of CPUs.

In order to avoid vivid performance drops because of deeper pipeline Intel has been constantly improving its NetBurst Pentium 4 processors. To accomplish this with Prescott, the Santa Clara, California-based chipmaker incorporated a number of important improvements into the chip. One is more efficient branch-prediction mechanism minimizing a number of situations when microprocessor has to reload its pipeline. Another one are enlarged caches that allow CPUs to handle more data “onboard” spending less time pumping data via processor system bus. Nevertheless, it is still to be found out how Prescott and Northwood chips behave on the same frequency.

Additional information on performance and architecture of Intel Pentium 4 “Prescott” will be available at launch, on the 2nd of February 2004.